Bush Meat Can Be a Potent Source of Viruses that Cross the Species "Barrier" and Threaten Human Health

Prior posts have noted the animal origin of many diseases that adversely impact humans (e.g., measles, chicken pox, H5N1 "bird flu"); a recent devastating example, of course, is HIV. Some of these diseases, like HIV and measles, diverged from their animal progenitor such that they are independently sustained within the human population.

Some wild animal populations are threatened, either locally or as a species, by hunters who acquire them for "bush meat". Such food can be a source of viruses that can cause disease or even initiate a virus that can infect humans in an ongoing basis. Yet, this risk has received little publicity, especially in regions in which such hunting occurs or even in urban areas (both locally and worldwide) in which such meat is sold. This risk is not insubstantial; nearly 75 percent of emerging infectious diseases in humans comes from animals, mostly wildlife (see, for example, http://wwwnc.cdc.gov/eid/, Emerging Infectious Disease, & http://www.niaid.nih.gov/topics/emerging/pages/default.aspx).

A new study now finds that meat from nonhuman primates (from chimps to monkeys) can host potentially dangerous viruses, which given the history of HIV should not be a surprise. The samples that were tested were confiscated at U.S. airports. Researchers analyzed primate and rodent bushmeat that had been serendipitously caught at five airports (JFK, Philadelphia, Washington, Atlanta, and Houston) over the past five years.

The samples ranged from raw to smoked; even smoked meat was found to contain viruses. The researchers focused on pathogens with a known potential to infect humans. Although the 35 rats hosted none of the viruses targeted for detection by the researchers (e.g., anthrax, coronaviruses), the nine primates did show viral contamination, sometimes from multiple viruses. To the extent the research can be said to have provided some good news, it was that none of the infectious agents that over the years have given rise to HIV/AIDS (simian immunodeficiency viruses) and to human T-lymphotropic viruses were found. But, do not get all happy about this. These viruses are known to infect African primates in great number. Thus, the researchers conclude that their failure to detect these viruses arises from the paupacy of samples that they had available for analysis.

The new analysis did turn up substantial contamination of the non-human primates with herpesviruses (e.g., cytomegalovirus, lymphocrptovirus). Cytomegalovirus normally causes few symptoms in people except when infection occurs during fetal development or among individuals with a compromised immune system. Lymphocryptoviruses includes a family of viruses (the best-known being the Epstein-Barr virus) that have been associated with serious infections and tumors in people.

The simian foamy virus was found in the bushmeat samples. A retrovirus, it belongs to the same overarching family of disease-causing agents as HIV and human T-lymphotropic viruses (which has been linked with neurological impairments and blood cancers). Both HIV and HTLV appear to have arisen when infection with largely benign primate versions of the viruses did not prove to be benign in humans.

Retroviruses tend to become lifelong infections that develop slowly and may be hard to spread. In the case of simian foamy virus, CDC has been following groups of people that picked up foamy virus infections in the United States and Africa from monkeys and apes that they had hunted, butchered, eaten, or had frequent contact with (e.g., vets, zookeepers, and pet owners).

In more than a dozen years of followup, no one with simian foamy virus has yet exhibited disease symptoms - which might be taken as a sign that this virus is not very dangerous, but that conclusion would be premature. Researchers suspect that the infected patients may not have been followed long enough yet to identify any slowly developing disease or immune impairment. Other well known viral diseases can take decades to manifest disease in human (such as HTLV, which can ultimately cause leukemia, lymphoma, inflammatory diseases such as arthritis, and potentially debilitating neurologic disorders affecting the spinal cord).

Not surprisingly, researchers want to broaden their search for these potentially harmful viruses.

Clearly, there is a benefit in joining species preservation with condemnation of the taking and consuming of bush meat.